1. Field of the Invention
The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus, in which parasitic plasma is not generated in a transfer chamber.
2. Description of the Related Art
Generally, plasma processing apparatuses are used to process a substrate, such as etching, for flat panel displays, which is supplied thereto, using plasma. The flat panel displays include liquid crystal displays, plasma display panels, or organic light emitting diodes. Among these plasma processing apparatuses, a vacuum processing apparatus generally includes three chambers, i.e., a load lock chamber, a transfer chamber, and a processing chamber.
The load lock chamber serves to receive a non-processed substrate from the outside or discharge a processed substrate to the outside alternately in an atmospheric state and a vacuum state. The transfer chamber is provided with a transfer robot for transferring a substrate between the other chambers, and serves to convey a substrate to be processed, from the load lock chamber to the processing chamber or a processed substrate from the processing chamber to the load lock chamber. The processing chamber serves to deposit a film on a substrate or etch a substrate using plasma in a vacuum.
The processing chamber is provided with electrodes installed at the upper and lower parts of the inside thereof. Generally, one electrode of the processing chamber is connected to a RF power source, and the other electrode of the processing chamber is grounded. When RF power is applied to the inside of the processing chamber under the condition that a processing gas is injected into the processing chamber, plasma is generated in the processing chamber due to electric discharge, and a substrate is processed using the plasma.
As shown in FIG. 1, a conventional plasma processing apparatus includes a load lock chamber 10, a transfer chamber 20, and a processing chamber 30. Gate valves 40 and 50 are provided between the load lock chamber 10 and the transfer chamber 20 and between the transfer chamber 20 and the processing chamber 30 under the condition that the gate valves 40 and 50 are adjacent to the corresponding chambers 10, 20, and 30.
The gate valve 40 is interposed between the load lock chamber 10 and the transfer chamber 20, and serves to open and close a communication channel therebetween. The gate valve 50 is interposed between the transfer chamber 20 and the processing chamber 30, and serves to open and close a communication channel therebetween. The gate valves 40 and 50 include valve housings 42 and 52, valves 44 and 54, and valve driving units 46 and 56.
The airtightness of the valve housing 42 between the load lock chamber 10 and the transfer chamber 20 is maintained by airtightness maintaining members (O), and the airtightness of the valve housing 52 between the transfer chamber 20 and the processing chamber 30 is maintained by airtightness maintaining members (O).
Plates for opening and closing openings of the load lock chamber 10 and the transfer chamber 20 by means of the valve driving unit 46 are provided in the valve housing 42, and plates for opening and closing openings of the transfer chamber 20 and the processing chamber 30 by means of the valve driving unit 56 are provided in the valve housing 52.
The transfer chamber 20 is provided with a transfer robot 22 installed therein for transferring a substrate (not shown) to the load lock chamber 10 or the processing chamber 30. The transfer robot 22 includes a transfer arm and a driving unit (not shown). The transfer arm includes an end effector assembly 24, and an end effector 26 connected to the end effector assembly 24 for transferring the substrate.
Generally, chambers are made of aluminum. However, the transfer chamber 20 is made of steel use stainless (SUS) due to strength to weight ratio and increase in volume corresponding to the size of a substrate.
The transfer chamber 20 made of SUS, which has specific resistance differing from that of aluminum, is not easily grounded. When the transfer chamber 20 is not completely grounded, as shown in FIG. 2, RF power (R) in the processing chamber 30 is not exhausted to the outside, but is induced in the transfer chamber 20. When the RF power (R) is induced in the transfer chamber 20, the wall of the transfer chamber 20 does not reach a complete grounding potential state, and the wall of the transfer chamber 20 and the corner portion of the end effector assembly 24 having a grounding potential, which is disposed close to the wall of the transfer chamber 20, are coupled, thus generating parasitic plasma (PA).
When parasitic plasma (PA) is generated in the transfer chamber 20, many problems occur. That is, processing characteristics are changed due to an RF power loss, particles are increased due to damage to ions in the transfer chamber 20, static electricity of a substrate is generated due to charging of the inside of the transfer chamber 20 or the transfer robot 22, and the transfer robot 22 malfunctions due to the pseudo noise of RF.